1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) technology field, more particularly, to a thin film transistor (TFT) switch and a method for manufacturing the same.
2. Description of the Prior Art
In detection of an LCD panel, there are two common designs for detecting circuits. One is that a detecting circuit is directly coupled to scanning lines or data lines in a display area of the panel, and it needs to cut a connection between a test circuit and a circuit in the display area by using laser after the detection. The other is that the test circuit is coupled to a signal line in the display area via a TFT switch. Signal is fed to the display area through the TFT switch when a high voltage level is applied on a gate of the TFT switch to turn it on. On the contrary, since the TFT switch turns off for disconnection between the test line and the scanning or data line in response to a low voltage level applied on the gate of the TFT switch when the panel operates normally, a process of laser cutting is therefore omitted.
Conventionally, there are three electrodes of the TFT switch for detecting circuits, i.e. a gate, a drain and a source. The gate of the TFT is in negative bias in a long term when the panel works normally, and therefore electrical characteristic of the semiconductor layer of the TFT varies to increase leakage current. FIG. 1 shows a circuit diagram of a conventional switch TFT. As FIG. 1 shows, a shorting bar is connected to drains 11 and 14 of the two TFTs. Sources 12 and 15 of the two TFTs are respectively connected to different scanning lines (GL) or data tines (DL). When two gates 13 and 16 of the TFTs are applied at a low voltage, the two TFTs switch off. If a leakage current passing through the two TFTs and the shorting bar occurs, a short circuit between the different scanning lines or data lines, i.e. a short circuit between different signals, happens and deteriorates display quality.